I wanna hire a PHP programmer to install 2 PHP scripts (Gripsell and iSocial) and make it so that when someone signs up, they can use both with 1 login. How easy / difficult is this to do - how many hours are we talking here, and are there any roadblocks? Thanks team!
Since neither one is free, you're going to have to buy them, then give them to your programmer to give you an estimate. It's like telling your car mechanic that your car won't start, and asking how much the repair will be. For fixing a loose battery connection or for rebuilding a seized engine? There's no generic "make 2 scripts work with a single login" code. The logins of both scripts have to be modified so that if you log into one script, the other script considers you logged in. Depending on how one or both scripts are written, that can range anywhere from a lot of work to "you couldn't afford it unless you won the lottery". I CAN tell you one thing - it's not trivial or cheap.
You could probarly try to use one table for users/registration. In that way, one registration works both ways.
Halvin, that allows the user to log into either script using the same username and password. I think what the OP wants is that if you log into one of them, then go to the other one, you're already logged in. Like log into Gripsell, then click on a link to iSocial and you're already logged into iSocial. The only way to tell how much work that would be is to look at both scripts, and anyone competent would want to be paid for that work, even if the OP decided not to have any further work (like writing the code) done. This isn't something you can do in 15 minutes - it's going to take time and effort, and very few competent people work for free.